Characteristics of electron-beam-excited Xe*2 at low pressures as a vacuum ultraviolet source

Abstract

The performance of Xe*2 as a 172-nm fluorescence or laser source when pumped by a low-current, long-pulse electron beam was determined. The fluorescence efficiency of Xe*2 is near the theoretical limit of ∼50% at modest pressures over a range of pump rates up to 106 W/cm. The laser efficiency is limited to values <1% by a very strong medium absorption that is probably due to Xe*2 photoionization. Laser performance is further degraded by early pulse termination that appears related to mirror degradation. An improved kinetics and extraction code was developed to model the performance of the Xe*2 system. A key component of the model is a more detailed treatment of the interactions between secondary electrons and excited atomic and molecular xenon states. Rates for these processes were derived as described herein. With this model, good absolute agreement was obtained between experiments and calculated parameters at pressures as low as 0.5 atm.